Field of the Invention
The present invention relates to yogurts containing reduced levels of protein. More particularly, the present invention is directed towards yogurts having reduced protein levels (and thus reduced cost to manufacture) supplemented with a starch based texturizer that enables the yogurt to retain its texture characteristics (e.g., viscosity) and stability (e.g., against syneresis after seven weeks of storage) comparable to full protein yogurt products.
Yogurt is a nutritious dairy product which has become quite popular within the last 30 to 40 years. Yogurt is produced by culturing a dairy ingredient (cream, milk, partially skimmed milk, skim milk or combinations thereof) with a bacterial culture containing the lactic acid producing bacteria Lactobacillus bulgaricus and Streptococcus thermaphilus. Other cultures can also be used in addition to these two.
Yogurt can optionally contain other ingredients such as vitamins (e.g., vitamin A and/or D), as well as ingredients to increase the nonfat solids content of the yogurt such as concentrated skim milk, nonfat dry milk, buttermilk, whey, lactose, lactalbumins, lactoglobulins and/or other milk solids. Other optional ingredients include sweeteners, flavoring ingredients, color additives and stabilizers.
Yogurt is available in a wide assortment of textures, fat content and flavors, among other attributes. For example, yogurt contains, before the addition of bulky flavors, not less than 3.25% milkfat, and not less than 8.25% milk solids-not-fat. Low-fat yogurt contains from 0.5% to no more than 2% milkfat before the addition of bulky flavors, and nonfat yogurt contains less than 0.5% milkfat before the addition of bulky flavors. These amounts can vary depending upon local regulations.
Yogurts generally fall into one of three styles, namely, Balkan-style or set-style yogurts, Swiss-style or stirred yogurts, and Greek-style or Mediterranean (strained) yogurts. Set-style yogurts are made by pouring the warm cultured milk mixture into containers and then incubating the mixture without any further stirring. Set-style yogurts have a characteristically thick texture. Stirred yogurts are made by incubating warm cultured milk mixture in a vat, cooling the mixture, and then stirring the cooled mixture for a creamy texture, often with fruit, fruit preparations or other flavorings added. Stirred yogurts are often slightly thinner than set-style yogurts. Greek-style or Mediterranean yogurt is made by either removing some of the water from the milk or by straining whey from plain yogurt to make it thicker and creamier.
The gel structure of set-style yogurts results from an acid-casein interaction, wherein casein (protein) micelles at or near their isoelectric point flocculate, and the colloidal calcium phosphate partially solubilizes as acidity increases. During fermentation of the milk, the pH gradually declines to around 4.5, and destabilized micelles aggregate into a 3-dimensional network in which whey is entrapped. Appearance of whey on the surface (“wheying-off”) is due to syneresis.
In stirred-style yogurt, the 3-dimensional network is disturbed when fruit and flavors are mixed into the plain yogurt. Texture and physical properties of stirred-style yogurts is therefore determined by the fruit, stabilizer and rate of cooling in their manufacture.
Stabilizers are often added to prevent surface appearance of whey, as well as to improve and maintain body, texture, viscosity and mouthfeel. Examples of stabilizers include gelatin, whey protein concentrates (‘WPC’), gums (e.g., locust bean gum, guar gum, carrageenan and xanthan), protein and starch, including modified starch. Yogurts having lower or reduced milk solids have a greater tendency to synerese; therefore, stabilizers are often added to such yogurts. Often a combination of stabilizers is added to the yogurt formulation to avoid defects that may result from the use of just one stabilizer.
Full protein yogurts typically contain about 3.3% to about 3.5% protein (whey and casein) in the starting milk, and around 8.2% dairy solids (protein, lactose, fat, etc). In many countries, a substantial portion of the population cannot afford yogurts such as those described above. Therefore, in order to make these yogurts more affordable, manufacturers often dilute the yogurt with water. However, this dilution is problematic in that, depending upon the degree of dilution, it reduces the amount of milk solids, which negatively affects the properties of the yogurt (e.g., viscosity, texture, mouthfeel, etc.). As noted above, the acid-casein interaction in the yogurt gives it its gel structure. Adding water to the overall formulation reduces the total amount of protein in the yogurt, resulting in a less viscous yogurt.
Certain additives such as powdered milk can be added to this diluted yogurt formulation to provide benefits such as texture and/or viscosity; however, use of these additives come at an increase in their cost of manufacture. Other additives such as gums or gelatin can be used to improve viscosity of the diluted formulation; however, use of these ingredients can result in a yogurt with an unpleasant mouthfeel as well as added cost of manufacture. Therefore, there is a need for texturizers and/or viscosifiers that can replace or supplement the added protein in powdered milk for these yogurts, thereby providing the organoleptic benefits provided in an undiluted formulation containing the full amount of protein, yet without a substantial increase in the cost of manufacture.
While yogurts with moderate or high levels of protein are well known, there is a demand, particularly in developing countries, for yogurts that have reduced protein levels (and thus reduced cost to manufacture) yet retain the texture characteristics (e.g., viscosity) and stability (e.g., against syneresis after seven weeks of storage) of full protein products.